Yes, the user licenses (timesheet/expense user, scheduling user or admin/invoice user) in your monthly subscription are linked to your account subscription, not the employee they are assigned to.
You can un-assign a license from a user as needed or archive the contact to free up the license, and re-assign them to new employees if required. You should still be able to view all the history in terms of timesheets, tasks, and expenses for the user you have taken the license away from.
Read more about archiving and un-archiving users.
Do you need further help with this? Feel free to contact our support team via chat or email (firstname.lastname@example.org).